The substrate thicknesses in modern semiconductor packages have continued to shrink so that mobile devices may have a thinner profile. In addition, system designers require a reduced surface-area footprint for the semiconductor packages. The need to integrate passive devices into a system is one issue that limits component density. In that regard, it is relatively straightforward to surface mount a discrete passive device such as a surface-mount (SMT) capacitor or inductor to a printed circuit board or package substrate. But such a mounting then demands more circuit board or substrate surface area and thus increases the overall footprint of the resulting electronic system. Another issue with surface mounting is that glass-based interposers and glass substrates have been increasingly used to support passive devices. Traditional mounting of SMT passive components onto glass raises reliability issues due to micro-cracks resulting in the glass from the associated drilling of holes and vias to support the surface mounting.
As an alternative, passive devices may be embedded within a cavity in the substrate. But to achieve thinner device profiles, substrates have been progressively thinned such as to no more than 200 microns. A typical embedded passive device has a height of at least 150 microns such that there is not sufficient room to embed such a device into a relatively-thin substrate.
Accordingly, there is a need in the art improved embedded passive devices.